diff --git a/frigate/http.py b/frigate/http.py
index 17fdb327a..c599a8f5f 100644
--- a/frigate/http.py
+++ b/frigate/http.py
@@ -603,7 +603,9 @@ def event_preview(id: str, max_cache_age=2592000):
         )
 
     start_ts = event.start_time
-    end_ts = min(event.end_time - event.start_time, 20) if event.end_time else 20
+    end_ts = (
+        start_ts + min(event.end_time - event.start_time, 20) if event.end_time else 20
+    )
 
     if datetime.fromtimestamp(event.start_time) < datetime.now().replace(
         minute=0, second=0